A study of the properties of membrane-bound receptors and enzymes in skeletal muscle sarcolemma in normal, denervated and dystrophic states will be undertaken. Two different acetylcholine isoreceptors will be separated and characterized with respect to; kinetics of alpha-bungarotoxin binding; binding to carbohydrate specific lectins; distribution in fast and slow muscle fibers, and time course of appearance after denervation and after muscle inactivity caused by nerve block. The two isoreceptors are present in mixed-fiber muscles in equal amounts at 14 days after denervation and differ from junctional receptors. An enzyme present in normal muscle which metabolizes extrajunctional, but not junctional receptors, will be purified. Antibodies to receptors will be separated into antigen specific IgG's directed against different subunits of the receptor. "Receptor-like" antigens anti-receptor IgG will be purified and characterized. Basic studies on properties of sarcolemma-bound adenylate-cyclase, protein kinase and its endogenous protein substrate will be done, and identification of a membrane phosphoprotein phosphatase activity will be undertaken. The relationship of protein kinase activity and phosphorylated membrane state to calcium binding by sarcolemma will also be studied.